Active material

ABSTRACT

An active material is disclosed in the present invention. The active material includes a lithium active material and a complex shell which completely covers the lithium active material. The complex shell includes at least one protection covering and at least one structural stress covering. The protection covering is a kind of metal which may alloy with the lithium ion. The structural stress covering dose not alloy with the lithium active material. The complex shell efficiently blocks the lithium active material out of the moisture and the oxygen so that the lithium active material is able to be stored and operated in the general surroundings. The structural stress provided via the structural stress covering may keep the configuration of the active material unbroken after the repeating reactions.

This application claims the benefit of priority based on Taiwan PatentApplication No 103124345, filed on Jul. 16, 2014, the contents of whichare incorporated herein by reference in their entirety.

BACKGROUND

1. Technical Field

The present invention is related to an active material, in particular toan active material comprising the lithium metal.

2. Description of Related Art

In order to provide the power, the proper active materials must beapplied for the power supply system to convert the chemical energy intothe electrical energy. For example, the common active materials appliedfor the lithium battery contain the lithium, carbon and so on, whereinthe lithium metal has the highest energy density. However, the lithiummetal has high chemical activity so that the storage and operationconditions must be maintained severely since the lithium metal reactswith the oxygen and moisture in the surroundings immediately aftercontacting. The conditions of storage and operation must be controlledin low moisture, few oxygen and proper temperature and humidity so thatthe cost of process gets higher. Since, the lithium metal is so active,the excite oxidation-reduction reaction occurs under improperconditions, which sometimes would turn into the combustion reaction.

As known, in order to increase the reaction surface area of theelectrode of the power supply system, the particle size of the lithiumis in the scale of micrometer or nanometer. A lithium carbonate shell isexerted for covering the lithium metal in the scale of micrometer ornanometer for solving the difficulties in storing and operating.However, the smaller the particle is the severer reaction occurs. Hence,during the slurry mixing, the low-polarity solvent, such as toluene, isrequired to avoid the reaction between the lithium and the NMP/PVDFsolvent. But the low-polarity solvent is harmful for the human and theenvironment.

Accordingly, an active material is provided to overcome the aboveproblems.

SUMMARY OF THE INVENTION

It is an objective of this invention to provide an active material. Acomposite layer, which comprises at least a protection layer and atleast a structural layer, covers the lithium active material entirely.The composite layer blocks the moisture and the oxygen from thesurroundings so that the high reactive lithium active material can bestored and operated under the normal condition. The dependence of thestorage and/or operation conditions of the active material having thelithium metal can be decreased.

It is an objective of this invention to provide an active material. Thecomposite layer covering the lithium active material can provide higherionic conductivity and structural strength so that the reactedprotection layer can be confined to a certain area instead of being faraway the lithium active material. The structure of the active materialwould not break down due to the loosen structure of the protection layerafter the repeating alloying/de-alloying reaction.

It is an objective of this invention to provide an active material. Theprotection layer of the composite layer comprises a first protectionmaterial and second protection material. The first protection materialand the second protection material can be alloyed metal and/ornon-alloyed metal. The content of the metal that can alloy with thelithium metal and/or the lithium ion is not less than 0.1%.

It is an objective of this invention to provide an active material. Thelithium active material and the protection layer are separated via thebarrier layer, which is disposed between the lithium metal layer and theprotection layer of the composite layer. No unexpected reactions, suchas the alloy reaction, would occur in the contacting interface betweenthe lithium active material and the protection layer before expectedreactions start.

The present invention discloses an active material comprising a lithiumactive material and a composite layer covering the lithium activematerial entirely. The composite layer comprises at least a protectionlayer and at least a structural layer. The protection layer has at leasta metal which is able to alloy with the lithium; the structural layer,on the other hand, does not alloy with the lithium metal and/or thelithium ion. The composite layer effectively blocks the lithium activematerial from the surroundings so that the moisture and the oxygen wouldnot contact with the lithium active material. The active material havingthe composite layer disclosed in the present invention can be stored andoperated under normal condition. The structural stress of the structurallayer can provide a buffer for sustaining the loosen structure of theprotection layer after the alloy reaction and avoid the structurebreakdown.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow illustration only, and thus arenot limitative of the present invention, and wherein:

FIG. 1A illustrates the active material of this present invention.

FIG. 1B illustrates the active material of this present invention.

FIG. 1C illustrates the active material of this present invention.

FIG. 2A illustrates the active material of this present invention.

FIG. 2B illustrates the active material of this present invention.

FIG. 3A illustrates the active material of this present invention.

FIG. 3B illustrates the active material of this present invention.

FIG. 3C illustrates the active material of this present invention.

DETAILED DESCRIPTION

The present invention discloses an active material applied in the powersupply system having dissociated ions such as lithium battery. Theactive material comprises a lithium active material entirely covered viaa composite layer comprising at least a protection layer and at least astructural layer. The composite layer effectively blocks the moistureand the oxygen from the lithium active material via the proper materialsand the relative locations of the protection layer and the structurallayer. The active material of the present invention can be stored andoperated under normal condition. Besides, the loosen protection layer,after repeating reactions, could be confined to the composite layerinstead of being far away from the lithium active material so that thereversible efficiency of the protection layer can be increased and thegreat amount of the structure breakdown of the active material of theelectrode would be avoided.

The protection layer and the structural layer are described hereinafter.

The protection layer must have at least a metal which is able to alloywith the lithium active material and/or the dissociated ions (ex.lithium ions). The structure of the protection layer becomes loosenafter alloying reaction, wherein the loosen structure provides paths forthe dissociated ions and the lithium active material to proceed theelectrical-chemical reaction. The protection layer blocks the moistureand the oxygen in the surroundings from the lithium active materialbefore the active material is assembled into the power supply system.Accordingly, the moisture and oxygen in the surroundings would notcontact with the lithium active material so that no severeoxidation-reduction reaction occurs due to the protection layer.

The structural layer must have a higher structural strength to sustainthe structure deformations (ex. loosen lattice due to alloying reaction)of the protection layer and/or the lithium active material. Also, thestructural layer can serve as the concluding points of the adhesion ofthe active material so that the deformation of the active material wouldnot lead to the structure breakdown of the electrode. The structurallayer has some ionic conductive regions for ions to migrate into theprotection layer to proceed the oxidation-reduction reaction. Further,the structural layer has the ability of electrical conducting so thatthe inner resistance of the active material can be reduced.

Accordingly, the present invention is disclosed in detail.

Referring to the FIG. 1A, an embodiment of the active material of thepresent invention has been illustrated.

As illustrated, the active material 10 comprises a lithium activematerial 12, a composite layer 14 covering the lithium active material12 entirely. The composite layer 14 comprises a protection layer 142 anda structural layer 144.

The protection layer 142 is disposed next to the outer surface of thelithium active material 12 and entirely covers the lithium activematerial 12. Accordingly, the lithium active material 12 is completelyisolated from the moisture and the oxygen of the surroundings so thatthe severe oxidation-reduction reaction can be avoided.

The structural layer 144 at least partially covers the outer surface ofthe protection layer 142. The alloyed protection layer 142 and thelithium active material 12 are confined to a certain area due to thestructural layer 144. Moreover, the structural layer 144 covers on theouter surface of the lithium active material 12 so that the structurallayer 144 can increase the structural strength, especially when thestructure of the alloyed protection layer 142 becomes loosen, and canconfined the alloyed materials closer to the un-reacted protection layer142. Once, the de-alloying reaction occurs, the loosen alloyed materialswould not be far away from the protection layer 142, hence, the alloyedmaterials may proceed the alloying reaction in the region closer to thelithium active material 12 and the un-reacted protection layer 142 sothat the alloyed materials can be reacted under the proper operationvoltage. Besides, due to the function of confining the alloyedmaterials, the electrical conductivity and the ionic conductivity of theactive material 10 can both be remained via the structural layer 144even after several times of the alloying/de-alloying reactions.

The lithium active material 12 is made of a material selected from thegroup consisting of the lithium metal, the lithium compound or thecombination thereof. The lithium active material 12 can be in the shapeof granule, sheet and/or any shapes. The protection layer 142 comprisesat least a metal. And, of course, a plurality of metals can be includedas well. The dissociated ions can be the lithium ions for the case ofthe lithium battery. Accordingly, the metal of the protection layer 142can be selected from the group consisting of aluminum, tin, alloyedaluminum, alloyed tin and/or a lithium-alloyable metal/alloy. Thedissociated ions can be provided via the medium such as the conventionalelectrolyte exerted in the power supply system. For example, the mediumcan be selected from the group consisting of liquid-phase electrolyte,solid-phase electrolyte, gel electrolyte, liquid ion, organic solventwith lithium salt, inorganic solvent with lithium salt or a combinationthereof.

A lithium battery is taken as an example for the power supply systemhereinafter. The protection layer 142 of the active material 10 isalloyed with the lithium ions (i.e. dissociated ions) provided via theelectrolyte (i.e. the medium) of the lithium battery and/or is alloyedwith the lithium metal formed on the surface of the protection layer 142via lithium ion reduction. The alloyed materials have loosen and swelledlattices so that the protection layer 142 of the active material 10gradually breaks down. However, based on the main function of theprotection layer 142, it is clear to realize that the protection layer142 is exerted to protect the lithium active material 12 from themoisture and the oxygen of the surroundings before the active material10 is sealed inside the lithium battery. Once the active material 10 issealed inside the lithium battery, the lithium active material 12 canonly contact with fewer moisture and oxygen, so even the protectionlayer 142 swells and/or breaks down due to alloying/de-alloyingreactions, the protection provides via the protection layer 142 to thelithium active material 12 is not be affected substantially.

However, as for the conventional active material, the breakdown of theprotection layer still does have some influences of the performance ofthe active material. It is because that the conventional active materialis not covered via the structural layer on the outer surface such thatthe alloyed materials cannot be confined to a certain area and would bedistributed over the electrolyte and/or be formed as the loosenmaterials. Once, the more alloyed materials are formed, the poorerelectrical conductivity and ionic conductivity are gained. The activityof the active material is decreased and the polarity issue becomes moreseverely. In other words, the alloyed protection layer decreases thedegree of alloying reaction (i.e. decreases the rate of theoxidation-reduction reaction) and it makes the reversible capacity ofthe lithium battery decrease after several times of thealloying/de-alloying reactions. Comparing to the present invention, theconventional active material is covered via the protection layer only.Since the conventional protection layer serves as the concluding pointsof the active material and the electrode, the protection layer starts toswell and break down from its outer surface after several times of thealloying/de-alloying reactions. Apparently, the concluding points of theadhesion provide via the protection layer break down as well. At last,the active material would be peeled from the electrode and this wouldaffect the performances of the lithium battery. The active material 10disclosed in the present invention is covered via the structural layer144 on the outer surface so that the alloyed protection layer 142 can beconfined to a certain area. Hence, the concluding points provided viathe protection layer 142 would not break down so that the activematerial 10 can adhere to the electrode tightly even after several timesof the alloying/de-alloying reactions.

Unlike the conventional active material, the structural layer 144 servesas the concluding points in the present invention. Meanwhile, thestructural layer 144 provides the structural strength (i.e. structurestress) of the active material 10 to maintain the shape and thestructure. The alloyed protection layer 142 can be confined via thestructural layer 144, which at least partially contacts with theprotection layer 142, after several times of the alloying/de-alloyingreactions. In this embodiment, the structural layer 144 partially coversthe protection layer 142 and covers the lithium active material 12indirectly. In other words, instead of covering protection layer 142entirely, the structural layer 144 can partially covers the protectionlayer 142 as long as the structure stress provided is high enough.

In this embodiment, the structural layer 144 can be a metal having highstructure stress and high electrical conductivity, for example, thestructural layer 144 can be made of copper. In order to provide theionic conductivity, the copper structural layer 144 does not cover theprotection layer 142 entirely and has some holes 16 and/or gaps to serveas the ion/electron paths for oxidation-reduction reactions, that is, toserve as the ionic conductive area. The protection layer 142 is exposedfrom the holes 16 and/or the gaps so that the dissociated ions cancontact with the protection layer 142 directly and alloys with theprotection layer 142 to form the loosen alloyed materials to expose thelithium active material 12 for the oxidation-reduction reactions.

Referring to the FIG. 1B, an active material of the resent invention isillustrated. The composite layer 14 is comprises a protection layer 142and a structural layer 144, which are interlaced. The configuration isbased on the structural layer 144 made of the material having nomoisture and no oxygen, such as copper, so that the structural layer 144can serve as a part of protection layer 142 before the lithium activematerial 12 is sealed inside the battery. The ionic conductivity of thestructural layer 144 of this embodiment can be provided via the adjacentprotection layer 142.

Referring to the FIG. 1C, an active material of the present invention isillustrated. The main difference between the embodiments of FIG. 1A andFIG. 1C is that the structural layer 144 is made of a porous material,that is, the structural layer 144 itself is a porous structure. Forexample, the proper materials can be selected from the group consistingof polymer, ceramic, fiber or a combination thereof. Except for havingthe ionic conductivity, the intrinsic property of the structural layer144 can be electrical conductive. In order to having the electricalconductive property, the structural layer 144 can be made of aelectrical conductive material or be made of an insulation materialcomprising some electrical conductive materials such as carbonparticles, metal powders and so on. Moreover, the solid electrolyteand/or the gel electrolyte can be filled into the holes of thestructural layer 144 or can be absorbed via the polymer structural layer144 via immerging.

The protection layer 142 of the active material 10 of the presentinvention comprises a first protection material and a second protectionmaterial, wherein the first protection material of the protection layer142 is able to alloy with the lithium metal and/or the lithium ions andthe second protection material of the protection layer 142 is not ableto alloy with the lithium metal and/or the lithium ions. The firstprotection material and the second protection material can be the metal,metalloid and/or alloy. The content of the first protection material isnot less than 0.1%, that is, the content of the material, which canalloy with the lithium metal and/or the lithium ions, is not less than0.1%.

The first protection material can be selected from aluminum, tin,silicon, alloyed aluminum, alloyed tin, alloyed silicon or other metal,metalloid and/or alloy materials. The second protection materialcomprises one kind of metal/metalloid/alloy material or more than onekinds of metal/metalloid/alloy materials such as copper, nickel, iron orthe combination thereof. The protection layer 142 can be a dual-alloymaterial, a triple-alloy material or a multi-alloy material. Forexample, tin is selected as the material which can alloy with thelithium metal and/or the lithium ions and nickel-tin alloy is selectedas the material which cannot alloy with the lithium metal and/or thelithium ions, wherein the content of tin is not less than 0.1%.

The protection layer 142 swells after alloying. The swelling degree canbe decreased via the addition of the second protection material becausethe second protection material cannot alloy with the lithium metaland/or the lithium ions, that is, the swelling volume mainly comes fromthe alloyed first protection material. The metal which cannot alloy withthe lithium metal and/or the lithium ions can effectively solve theswelling problem after alloying reaction and avoid the decrease ofreversible capacity.

Please refer to the FIGS. 2A and 2B, two embodiments of the activematerial of the present invention are illustrated. In FIG. 2A, thestructural layer 144 of the active material 10 comprises a plurality ofblind holes. Inside the blind holes, the lithium active material 12 isdisposed in the bottom of the holes and the protection layer 142 isdisposed above the lithium active material 12. In FIG. 2B, the lithiumactive material 12 and the protection layer 142 inside the blind holesof the structural layer 144 do not contact with each other. The blindholes of the structural layer 144 can be taken place via the throughholes.

The FIGS. 3A to 3C illustrate the active material 10 comprising abarrier layer 18. The barrier layer 18 separates the lithium activematerial 12 and the composite layer so that the barrier layer 18 cannotreact with the lithium and has the ability of electrical conductivityand ionic conductivity. The ability of electrical conductivity of thebarrier layer 18 can allow the electrons to get into the lithium activematerial 12 for proceeding the oxidation-reduction reactions. Theability of ionic conductivity of the barrier layer 18 can be providedvia the material exerted. Or the ions can reach to the lithium activematerial 12 via the alloyed materials of the protection layer 142 tolead the medium toward the barrier layer 18 and at last the potential ofthe whole active material 10 is the same as the potential of the lithiumactive material 12.

The barrier layer 18 is disposed next to the lithium active material 12or covers the outer surface of the lithium active material 12. Theprotection layer 142 is disposed next to the lithium active material 12or covers the outer surface of the lithium active material 12. In FIG.3A, the barrier layer 18 directly and entirely covers the outer surfaceof the lithium active material 12. In FIG. 3B, the barrier layer 18directly and partially covers the outer surface of the lithium activematerial 12. In FIG. 3C, the barrier layer 18 further comprises at leastan inert metal region 182 and at least a depletion region 184. The inertmetal region 182 is disposed on the outer surface of the lithium activematerial 12 and is lithium-unalloyable. The depletion region 184 isadjacent to the inert metal region 182 and disposed between thecomposite layer and the lithium active material 12. No matter what kindof embodiment, the lithium active material 12 and the protection layer142 of the composite layer are separated via the barrier layer 18 sothat the lithium active material 12 would not react with the protectionlayer 142 under the improper condition (ex. elevated temperature) beforethe Faraday reaction occurs to keep the protection layer 142 unreacted.

In FIG. 3C, the inert metal region 182 is made of metal which isselected from the group consisting of copper, nickel, iron, titanium,zinc, silver, gold, alloyed copper, alloyed nickel, alloyed iron or acombination thereof. The depletion region 184 is an empty space. Whenthe protection layer 142 and the lithium ions from the medium react toform the alloy materials, the depletion region 184 can provide a bufferfor the swelling volume and provide the ionic paths as well.

The ability of electrical conductivity of the barrier layer 18 ishelpful for the keeping the potential of the active material 10 almostequal to the potential of the anode system (i.e. anode electrode, notshown). Consequently, when the active material 10 is entirely sealedinside the power supply system and is provided a medium such asinjecting a liquid electrolyte, the active material 10 gradually absorbsthe medium. At this moment, the lithium active material 12 is ionicallyconductive so that the potential of the active material 10 is almostequal to the potential of the lithium active material 12. The lithiumions from the liquid electrolyte deposit uniformly and delicately on thesurface of the protection layer 142 and further alloy with theprotection layer 142 of the composite layer to form the small-articlealloyed materials. When the alloyed protection layer 142 breaks intosmall particles, the electrical conductive paths are formed and thebarrier layer 18 becomes the ionic conductive paths due to the liquidelectrolyte immerged (i.e. ions leading-in).

As for the properties of the material, the barrier layer 18 can be madeof an electrical/ionic conductive material in the shape of layerstructure. The material can be the electrical conductive polymer such asPA or any electrical/ionic conductive polymer. The barrier layer 18 canbe made of the porous electrical conductive material such as theinsulation polymer having the electrical conductive particles, whereinthe electrical conductive particles can be selected from the metalparticles or the non-metal particles. The ions for the lithium activematerial 12 can be provided via the electrical conductive materialthrough the protection layer 142. The holes or the depletion regions 184as illustrated in FIG. 3C of the barrier layer 18 can serve as the ionicpaths.

The reaction mechanism of the active material of the present inventionas illustrated in FIG. 1A is provided hereinafter.

At first, provide a medium to the active material 10 of the power supplysystem, for example, the medium could be a liquid electrolyte or aliquid ion. The step is to inject the electrolyte into the power supplysystem to make the active material 10 immerge in the electrolyte. Atthis moment, the electrolyte penetrates through the holes 16 of thestructural layer 144 and reaches to the surface of the protection layer142.

Then, charge the power supply system (i.e. the lithium battery) to makethe dissociated ions (i.e. the lithium ions) of the medium (i.e. theelectrolyte) alloy with the metal material of the protection layer 142so that the alloyed protection layer 142 gains ions.

For example, the lithium active material 12 is the lithium metal and thematerial of the protection layer 142 reacting with the lithium activematerial 12 is the aluminum metal. As charging the lithium battery,because the surface of the protection layer 142 would be wetted via theelectrolyte, as long as the potential reaches the lithium depositionpotential, the lithium ions deposit on the surface of the aluminum metalof the protection layer 142 and alloy with the aluminum to form theLi—Al alloy. The lattices of the Li—Al alloys are broken and loosen. Thestructural layer 144 covering the protection layer 142 and adhering tothe electrode material can confine the Li—Al alloys in a certain areainstead of randomly dispersing in the electrolyte. Hence, thedistribution of the lithium active material 12 in the electrode will notbreak down due to the alloyed protection layer 142.

Moreover, the loosen protection layer 142 further provides the ionicpaths for the lithium ions of the electrolyte to migrate into thelithium active material so that the potentials of both the activematerial 10 and the lithium active material 12 are the same. Apparently,no influence affects the follow-up oxidation-reduction reactions. Later,the lithium active material 12 serves as the conventional electrode ofthe lithium battery, which is able to receive and release the ions andelectrons, so that the other procedures are similar to the conventionalcharge/discharge procedures.

Accordingly, the active material disclosed in the present invention canbe stored and operated under normal condition because the highlyreactive lithium active material is covered via the composite layercomprising the protection layer and the structural layer. The cost forstorage and operation can be greatly decreased. Also, the operationbecomes more flexible and easier.

Besides, the structural layer disclosed in the present invention canconfined the alloyed materials formed from the protection layer in acertain area so that the alloyed materials remain close to the lithiumactive material during the follow-up charging and dischargingprocedures. The efficiency of the active material would not be decreaseddue to the structure breakdown of the active material. Meanwhile, thestable and great concluding force between the structural layer and theelectrode can also keep the distribution of the active material insidethe electrode even the structure of the protection layer breaks.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. An active material, adapted to a power supply element, comprising: a lithium active material; and a composite layer, entirely covering the lithium active material to block moisture and oxygen from the lithium active material, comprising: a protection layer that is disposed next to an outer surface of the lithium active material, that comprises a first protection material and that forms an alloy with lithium metal/ion; and a structural layer that at least partially covers the protection layer and that includes a plurality of holes to expose portions of the protection layer, wherein the structural layer does not alloy with lithium metal/ion and does not have ionic conductivity, and wherein the protection layer becomes loosened after an alloying reaction to provide paths for the lithium active material to proceed with an electrical-chemical reaction.
 2. The active material of claim 1, wherein the protection layer covers an outer surface of the lithium active material.
 3. The active material of claim 1, wherein the structural layer partially covers the outer surface of the lithium active material.
 4. The active material of claim 1, wherein the structural layer is made of metal selected from the group consisting of copper, nickel, iron, alloyed copper, alloyed nickel, alloyed iron, and a combination thereof.
 5. The active material of claim 1, wherein the lithium active material is made of a material selected from the group consisting of lithium metal, lithium compound, and a combination thereof.
 6. The active material of claim 1, wherein the first protection material of the protection layer comprises at least one of a metal and a metalloid.
 7. The active material of claim 6, wherein the at least one of a metal and a metalloid is selected from the group consisting of aluminum, tin, silicon, alloyed aluminum, alloyed tin, alloyed silicon, and a lithium-alloyable material.
 8. The active material of claim 1, wherein the protection layer further comprises a second protection material, and the first protection material and the second protection material are at least one of alloyed materials and non-alloyed materials, and wherein the first protection material has a content in the protection layer that is not less than 0.1% and the second protection material is lithium-unalloyable.
 9. The active material of claim 1, further comprises a medium to proceed with an oxidation-reduction reaction and to donate lithium ions for at least parts of the protection layer to be alloyed.
 10. The active material of claim 9, wherein the medium is made of a material selected from the group consisting of a liquid-phase electrolyte, a solid-phase electrolyte, a gel electrolyte, a liquid ion, an organic solvent with a lithium salt, an inorganic solvent with a lithium salt, and a combination thereof.
 11. The active material of claim 1, wherein the structural layer is electrically conductive.
 12. The active material of claim 1, further comprising a barrier layer that separates the lithium active material and the composite layer, and that is lithium-unalloyable.
 13. The active material of claim 12, wherein the barrier layer is electrically conductive.
 14. The active material of claim 12, wherein the barrier layer is ionically conductive.
 15. The active material of claim 12, wherein the barrier layer is disposed next to the outer surface of the lithium active material.
 16. The active material of claim 12, wherein the composite layer covers the outer surface of the barrier layer.
 17. The active material of claim 12, wherein the barrier layer is at least one of a conductive polymer and a porous conductive layer.
 18. The active material of claim 17, wherein the porous conductive layer is at least one of a polymer having conductive particles and a metal grid.
 19. The active material of claim 12, wherein the barrier layer comprises: at least an inert metal region, disposed on the outer surface of the lithium active material and lithium-unalloyable; and at least a depletion region, adjacent to the inert metal region and disposed between the composite layer and the lithium active material.
 20. The active material of claim 19, wherein the inert metal region is made of metal selected from the group consisting of copper, nickel, iron, titanium, zinc, silver, gold, alloyed copper, alloyed nickel, alloyed iron, and a combination thereof.
 21. The active material of claim 19, wherein the depletion region is an empty space. 